Abstract: Methods for producing protein C in transgenic non-human mammals are disclosed. The protein C is modified at the two-chain cleavage site between the light and heavy chains of protein C from Lys-Arg to R.sub.1 -R.sub.2 -R.sub.3 -R.sub.4 where R.sub.1 through R.sub.4 are individually Arg or Lys. DNA segments encoding modified protein C are introduced into the germ line of a non-human mammals, and the mammal or its female progeny produces milk containing protein C expressed from the introduced DNA segments. The protein C expressed from the introduced DNA segments has anticoagulant activity when activated. Non-human mammalian embryos and transgenic non-human mammals carrying DNA segments encoding heterologous protein C are also disclosed.